Hi Nicolas, I can reproduce your reboot loop! The problem is a bug in the fai-make-nfsroot script from FAI 6.2.2 which prevent the nfsroot root to build correctly.
The easiest way is to have FAI 6.2.2. installed on the host and use the fai-make-nfsroot from FAI 6.0 https://raw.githubusercontent.com/faiproject/fai/6.0/bin/fai-make-nfsroot Then make sure sysvinit-core systemd-sysv- IS included in /etc/fai/NFSROOT and recreate the nfsroot. That worked for me booting FAI with bullseye. Inside the nfsroot you will have FAI 5.10.3. -- regards Thomas